Well liner



A- S. CURLET June 14, 1966 WELL LINER 2 Sheets-Sheet 1 Filed May 2, 1961 wwvff 4.

A. S. CURLET June 14, 1966 WELL LINER 2 Sheets-Sheet 2 Filed May 2, 1961 United States Patent 3,255,821 WELL LINER Alexander S. Curlet, Pointe-a-Pierre, Trinidad. B.W.I., assignor to Texaco Trinidad, Inc, Pointe-a-Pierre, Trinidad, B.W.I., a corporation of Delaware Filed May 2, 1961, Ser. No. 107,180 8 Claims. (Cl. 16646) This invention relates to a liner for use in oil, gas or water wells, a device designed to promote the production of the desired fluids by screening and thereby preventing the entry into the well bore of sand and other finely divided solids from the producing formation. It also relates to a method of placing and cementing unit sections of the liner together and to the equipment assemblage to permit operation of a tubing string and pump inside the liner.

It is generally known that the production of fluids from an underground producing formation is often reduced or even completely choked off by the movement of sand and/or other finely divided solid materials into the well bore. Sand and finely divided solids are also troublesome when they are entrained in the produced fluids because of abrasion of pump parts and other equipment.

It is a general practice to employ strainers or screening devices, such as well liners, to overcome the above-noted problems. A wide variety of well liner devices have been devised to prevent the movement of sand and other materials into the producing zone of wells. Such devices usually consist of a perforated metal cylinder generally employed in association with a fine mesh screen. It is also common to supplement the function of the liner by placing it in a bed of packed gravel. Optionally, the packed gravel can be contained in an enclosure integrally associated with the liner having suitable openings to permit fluid communication with the producing zone.

The devices employed heretofore have not been entirely satisfactory for the purpose in question. pensive to manufacture and because of their rigidity are often difficult to install in a well bore. They are, moreover, subject to corrosion and as a result of this are costly to maintain. In addition, known well liner devices often restrict the well bore so that a pump cannot be run through the liner into the producing zone of the well. A further problem is that they are diflicult to remove from the well bore and being of metal cannot be readily drilled out of the well.

A well liner device has now been discovered which is highly effective as a strainer and which overcomes the drawbacks encountered with known well liner devices. This well liner is easily installed in a well bore and readily removed as will be more fully explained hereinbelow.

Briefly stated in accordance with this invention, there is provided a well liner device comprising comiminuted organic material that has been cemented into the desired size and shape. More particularly, the hard shell of nuts and of fruit pits which has been ground to specific particle sizes is cemented with an insoluble agent into the form of a hollow cylinder having porous walls with a permeability in the range of to 800 darcies.

The invention is illustrated in the accompanying drawings wherein:

FIGURES 1 and 2 are perspective views illustrating a preferred form of the liner in which the opposite ends are tapered such that successive liner units are readily nested.

FIGURE 3 is a longitudinal cross-sectional view of the embodiment of FIGS. 1 and 2 showing ball and joint type construction at the ends of the liner.

FIGURE 4 is an elevational view in partial longitudinal cross-section showing the lower end of one liner section nested in the upper end of a second liner section for use They are ex-' 3,255,821 Patented June 14, 1956 ice in service in which it is not intended to operate a pumping string inside the liner.

FIGURE 5 is a longitudinal cross-sectional view showing the lower end of one liner section nested in the upper end of a second liner section in an embodiment wherein the individual liner sections are composited or joined together at the well site prior to lowering into the well bore and wherein a pumping string is to be operated inside the liner.

FIGURE 5a is an axial cross-sectional view through section a-a' of FIGURE 5.

FIGURE 6 is an elevational view of the tubing end of portion of a self-aligning J tool.

FIGURE 7 is a longitudinal view, partly in cross section, showing an arrangement for sealing the top of the liner to the casing.

FIGURE 8 is an elevational view, partly in cross section, showing a multi-section liner in place in a producing formation in a tubing string positioned inside the liner for producing the well.

Referring now to FIGURE 1, a liner body 10 is shown in the form of a cylinder having outwardly tapered end wall 12 and opening 11 disposed along the axis of the cylinder.

In FIGURE 2, a cylindrical liner body 14 which is identical in construction with liner 10 of FIGURE 1, is illustrated showing an inwardly tapered end wall 15 and opening 16 disposed along the axis of the cylinder. The cross-sectional view in FIGURE 3 provides a better illustration of the preferred ball and socket type joints wherein the geometrical shape of outwardly tapered end wall 12 is identical with that of inwardly tapered end wall 15 such that adjacent sections nest together.

FIGURES 4 and 5 show two types of landing sections which may be used with the liner assembly in accordance with the present invention. FIGURE 4 shows a landing liner for use when it is not intended to operate a pumping string inside the liner, thus, liner body it is nested in liner body 14 by a tight fitting connection formed by outwardly tapered end wall 1-2 of liner 10 and inwardly tapered end wall 15 of liner 14. Both opening 11 of liner 10 and opening 16 of liner 14 form a continuous passageway through the assembled liner. The lower end of liner body 14 rests on the bottom of the well bore. If desired, it may be covered with an end plate, not shown in the figure.

FIGURE 5 shows a type of construction which may be employed where a composite of individual liner sections is assembled at the surface and lowered into the well bore as a unit for use where a pumping string is to be operated inside the liner. In this drawing the lower liner body 14 is shown as having a metal base plate 20 attached to the bottom thereof and an internally located landing guide nipple 21 having locking ports 22 for receiving latching pins located on a suitable mechanism attached to the end of a wire line or tubing string for lowering the assembled linerunits into a borehole. The metal plate 20 serves both to anchor the landing guide nipple 21 and to distribute tensional loads unifonmly across the cross sectional area of the liner material when the assembly is being lowered into the hole. The location of locking ports 22 is further shown in cross-section in FIGURE 50. Landing guide nipple 21 is further supported longitudinally by means of annular spacing element 23, which may be similar in composition to that of liner unit 14.

FIGURE 6 shows the lower end of a pumping string 41 'having attached thereto by means of sub 36 a I tool 37.

Guide plug 38 located at the lower end of 1 tool 37 enables the pumping string to be run easily into landing nipple 21 to assure centering of the pumping string within the liner sections. I

FIGURE 7 shows the apparatus used for placement of resin coated shell for sealing the top of the liner to the casing. The rubber cup forms a top seal between the tubing 34 and casing 32. Rubber cup 31 likewise forms a seal between tubing 41 and liner 33. Ports 34 on the side of tubing 41 are provided to permit an oil stream carrying the resin coated shell to be directed out of the ports 34 into the annulus 35 which it is desired to seal.

FIGURE 8 shows a series of liner units in combination with a string of tubing 41 in a well having a casing 42 and producing zone 43 characterized by consisting of unconsolidated material, such as sand and the like. This figure illustrates a liner of indefinite length prepared by joining a number of liner units together. liner units are generally required to communicate with the producing zone in a thick oil bearing formation.

A plurality of I Openings 43 are provided in casing 42 to permit the petroleum in formation 44 to pass through casing 42 to the liner 40. The figure also shows a J tool, such as is shown in FIGURE 6, located in position in the landing nipple shown in FIGURE 5.

The ground shell constitutes the bulk of the material in the composition of the liner. Coconut shell is the preferred shell material although other hard shells derived from walnut, nutmeg, brazil and pecan nuts as well as hard fruit pit sheels from peach, prune, plum and apricot pits may also be employed. The hard shell material is ground and size graded prior to its use. The particle sizes employed are selected to suit the particle size distribution of the solids to be screened but are in the range 8 to 80 mesh and generally close size cuts within the range 12 to 48 mesh as measured by U.S.S. (United States Standard) sieve sizes are preferred and satisfatcory. Mixtures of closely sizes graded shell within the above ranges may be employed in order effectively to screen very fine size solids and still to retain the high order of permeability indicated above.

As noted above, the composition of the well liner also comprises an insoluble binding agent or cement which serves to maintain or bind the ground shell in the desired shape. A wide range of insoluble thermosetting resins or cements may be employed for this purpose. Suitable thermosetting resins include the following kinds: phenolformaldehyde and modified phenol-formaldehydes such as resorcinol-rnodified phenol-formaldehyde, phenol-furfural, resorcinol-formaldehyde, novalak (which is mixed with formaldehyde or hexamethylene tetramine to achieve curing), urea-formaldehyde, melamine-formaldehyde, furan, unsaturated polyester (such as allyl diglycol carbonate), epoxy, and thermosetting copolymers of the foregoing or other resin types.

Advantageously, the phenol-formaldehyde and similar phenolic types are in the B state (resitol), that is they are condensed to a dense but workable stage (which can be solid or liquid). Unsaturated polyesters and epoxies are preferentially in the so-called p repolymer stage, that is they are viscous liquids ready for curing. The epoxy resins, such as one made from the condensation of bisphenol-A and epichlorohydrin, can be cured with an amine curing agent at low or elevated temperature, or crosslinked with phenolic, urea, or melamine resins at an elevated temperature of 300400 F. Unsaturated polyesters such as the linear condensation product of maleic or fumaric acid and a glycol suitably are mixed with a monomer such as vinyl acetate, methyl methacrylate, styrene or the like (which cross-links the unsaturated polyester chains) and cured in the presence of a peroxide catalyst. Thermosetting silicone or silicone-modified resins can also be used, particularly where high temperature resistance is desired especially.

It is essential that the insert well liner have the shape of a hollow cylinder with the opening disposed along the axis of the cylinder. It is a feature of this invention that the final long hollow cylinder desired is achieved as a multiple of identical unit sections. Neither the length nor the wall thickness of the unit sections are critical. Of all counts however it has been found practical to make the liner units about two feet long. Wall thickness is selected intelligently to suit the particular conditions with respectto casing size, production string size and total length of liner to be run bearing in mind the physical properties of the material of construction of the liner. Of course the outside diameter of the liner must be small enough for the liner to fit smoothly inside the well casing, but it is desirable that the clearance between liner and easing be kept small in the interest both of alignment of the liner when individual sections are run from surface, and to provide maximum latitude in determining wall thickness-bore relationship.

The ends of the liners can be of any shape which permits successive liner units to nest or fit closely together so that no space is left 'between adjoining unit sections which could be effective for sand entry. If desired the unit sections can be cemented together as an additional insurance against possible entry of sand at the junction of the unit sections. Ball and socket type joints can be employed at the opposite ends of the liner or the end walls can be tapered. In the latter instance, the wall at one end is tapered outwardly in the shape of a truncated cone while the opposite end wall is tapered inwardly parallel to the outwardly tapered end.

A feature of this invention is that a well liner of practically any required length can be fabricated and placed in position. In what is operationally the simplest procedure the individual liner units can be dropped into the well bore in such a manner that the individual units are nested one on top of the other when this operation has been completed. Where preferred a plurality of well liner units may be nested and cemented together at the surface and the composite structure then placed in the well bore.

A gap-filling cement or thermosetting resin similar to that described above may be employed to bond the liner units together in the .well bore. Cement or resin can be applied to the end surface or surfaces of each liner unit before it is dropped into position so that the units will be joined as they nest together. Care should be taken in selection of the cement such that the cement does not set before the units are nested together. This is readily accomplished with a knowledge of the time and temperature conditions to be experienced in the operations. Where the particular cement being employed contains a curing agent it may be considered desirable to utilize a separate application technique whereby cement and curing agent are each separately applied to matching ends of the liner units and therefore do not come into contact until nested.

An advantage of the present well liner is the high permeability of the liner to flow of a fluid therethrough. The well liners of this invention broadly have a permeability in the range of 10 to 800 darcies. The permeability is a function of the particle size or sizes of the liner material, such sizes being selected to suit the grain size of the formation material to be screened. A porous medium has a permeability of one darcy when the rate of flow through it, measured in milliliters per second per square centimeter of cross-sectional area, of a fiuid of one centipoise viscosity under a pressure of equivalent hydraulic gradient of one atmosphere (76 cm. of mercury) per centimeter is unity. See page 678 of Petroleum Production Engineering, by L. C. Uren, third edition, published by McGraw-Hill Book Company, Inc., 1946.

Well liner compositions having the requireddegree of permeability are prepared by combining the comminuted shell material with the cement within certain proportions. Effective proportions are determined by the specific surface, which is a function of the particle size, of the comminuted shell material. For the broad range of particle sizes likely to be used in practice these proportions may range from 5 to 35 weight percent of the binding agent combined with the balance or 65 to weight percent of the shell material. Ideally a thin glue line is desirable for both maximum strength and maximum permeability. For example for 12-20 mesh U.S.S. coconut shell the preferred proportions are binding agent to 90% shell material. Higher proportions of resin contribute nothing to strength and, compressed to achieve the desired thin glue line, can only result in some reduction in the permeability of the liner by being expressed into and blocking some of the interstitial space.

The well liners of this invention are preferably made in a mold having the desired dimensions to form a cylinder having a bore along the axis thereof. As an example, ground coconut shell of 12 to mesh and binding agent in the proportion of 8 lbs. of coconut shell and 0.8 lb. of urea-formaldehyde resin containing a fast-setting hardener were well mixed, introduced into a mold and then tamped or compressed Within the mold. The composition was permitted to cure for about an hour and then removed from the mold. After curing the liner exhibited very good physical properties. The compressive strength of liners prepared inthis manner is generally over 500 p.s.i. (pounds per square inch). The tensile strength of such liners is in excess of 100 p.s.i.

Well liners were prepared from ground coconut shell and urea formaldehyde resin. When 12-20 mesh shell was employed in the proportion of 90% weight shell to 10% resin the permeability was about 700 darcies. With 20-30 mesh shell in the proportion of 80% weight shell to 20% resin the permeability was about 300 darcies and with 30-48 mesh shell in the proportion of 80% weight shell to 20% resin the permeability was about 100 darcies.

It is to be noted that both the density of the component material, i.e. the individually resin coated shell grains (80 lbs./cu. ft.) and the bulk density (in air) of the liner material (40 lbs./ cu. ft.) are low and therefore advantageous with respect to achieving low falling velocities of the liner units when dropped freely in a liquid filled well bore.

In liner running practice it is conventional and normally necessary to use a liner seal arrangement whereby the annular space between the outside of the liner and the inside of the well bore casing is blocked off at the top of the liner so that no flow can take place into the well bore proper Without being screened through the liner. In the case of the present invention because of the close clearance between liner and casing and because of the high permeability of the liner, the same effect may be achieved by making the full liner section extend for some distance above the top of the perforated interval in the casing. Where, however, a liner seal is desired, conventional sealing devices may be used as with other liners but it is preferred in this invention to achieve the seal between the top of the liner and the casing wall by pumping resin coated coconut shell in oil to fill the space concerned.

Again in liner running practice it is conventional to seal the bottom of the liner and in the case of this invention this is achieved in one or other of two preferred ways. Where the liner units are to be run individually to nest on bottom and where it is not intended to operate a pumping string inside the liner the bottom seal is a shoe joint which is simply a standard liner unit but with the bore blanked off using the same permeable material of construction. Where it is intended to operate a pumping string inside of the liner and/or where it is preferred to make up the composite liner at surface before running into the well a special shoe joint is run which consists of a normal liner unit incorporating a bottom metalplate covering at least the full cross-sectional area of the liner and to which is attached one portion of a tubing latching device, such as a self aligning 1 tool as preferred here. Where the composite liner is to be made up at surface the shoe joint is attached to a joint of tubing through the 3 tool and liner units progressively spooled over the tubing until the full composite liner length is achieved when it is run on tubing to the bottom. of the hole and the tubing .6 string then released and retracted from the J tool. Where it is desired to pump inside of these liners the tubing string is run inside of the liner and connected to the shoe joint through the self aligning J tool. Thetubing string is then landed in tension when attaching to the casing head, the amount of tensional force being selected such as to prevent contraction and hence movement of the-tubing string when the fluid load is being taken off the tubing by the upward movement of the pumping rods, and not too much tensional force as to exceed the compressive strength of the liner material. The avoidance of movement or breathing of the tubing string is desired in order to overcome the risk of possible damageto the liner.

Example 1 Six liner units, the first a shoe joint, each two feet-long, 5.675" OD. and 3.5" 1D. and with matched ball and socket ends made to a 4" radius were dropped freely through a casing string comprised of 3,000 feet of 20 lbs/ft. 6 /s" casing (I.D. 6.049) and 100 feet of 28 lbs/ft. 6 /s" casing (LD. 5.791") to finish in nested relationship on bottom within the 28 lbs/ft. 6%" casing.

Example 11 251 liner units, the first a shoe joint, each 26% long, 8.75 OD. and 6'' ID. and with matched ball and socket ends made to 6" radius were dropped freely through a casing string comprised of 1,635 feet of 36 lbs/ft. 9% casing (I.D. 8.921") to finish in nested relationship on bottom.

I claim:

1. A well liner consisting as the complete structure of comminuted shell cemented with an insoluble binding agent, said liner being a self-supporting cylinder having a bore disposed along the axis thereof and characterized by having highly permeable exterior and interior cylindrical walls of the cemented comminuted shell free from any confining supporting metal structure and of sufficient strength in the comminuted shell structure per se to Withstand use within a well bore.

2. A liner according to claim 1 consisting of from 65% to comminuted coconut shell with the balance being an insoluble binding agent, said liner having a permeability within the range of from 10 to 800 darcies, a compressive strength over 200 p.s.i., and a tensile strength in excess of p.s.i.

3. A liner in accordance with claim 1 in which said insoluble binding agent is a urea-formaldehyde resin.

4. A liner according to claim 1, formed of a number of separate molded comminuted shell cylinders nesting one to another at the comminuted shell ends thereof to build up a liner of the required length, while each cylinder imparts sufiicient resiliency to the liner as a whole to facilitate installation within the well bore.

5. A well liner consisting as the complete structure of comminuted organic material selected from the group comprising the hard shell of nuts and of fruit pits and having a sieve size in the range of from about 8 to 80 mesh U.S.S. cemented with an insoluble binding agent, said liner being a self-supporting cylinder having a bore disposed along the axis thereof, said cylinder being free from any confining supporting metal structure characterized by having a permeability in the range of from about 10 to 100 darcies, a compressive strength over 200 p.s.i., a tensile strength in excess of 100 p.s.i. for the comminuted shell structure per se, and of suificient wall thickness to withstand use within a Well bore.

6. A well liner comprising a multiplicity of individual units, including a lower unit and one or more upper units, wherein said units consist entirely of comminuted shell cemented with an insoluble binding agent, said units being a self-supporting cylinder having a bore disposed along the axis thereof and characterized by having highly permeable exterior and interior cylindrical walls of the cemented comminuted shell free from any confining sup.-

7 porting metal structure and of sutficient strength in the comminuted shell structure per se to withstand assembly and use within a well bore, and wherein said bore of said lower unit is closed at one end thereof and said bore of said upper units is open at both ends of said cylinder.

7. The method in the treatment of a cased well bore containing liquid which comprises inserting liner sections having an outside diameter less than the inside diameter of the easing into the Well bore and having a bulk density in air of about forty pounds per cubic foot and a bulk density in water slightly higher than the density of water and consisting essentially of comminuted shell grains cemented together, the ends of said liner sections being coated with a thermosetting resin, and dropping the liner sections one by one by gentle free fall at low falling velocity to a predetermined location within the well bore to build up a liner therein by the sections coming to rest on top of one another such that the subsequent setting of said thermosetting resin at said location fastens said sections into a continuous rigid liner.

8. The method of installing a continuous well liner structure fabricated from a multiplicity of permeable well liner units in a liquid-filled well bore in an unconsolidated oil, gas or water bearing formation, each unit having a bulk density in air of about forty pounds per cubic foot and a bulk density in water slightly greater than the density of water and consisting essentially of comminuted shell grains cemented together, which comprises applying to the end walls of the said well liner units a hardenable thermo-setting resin unaffected by the presence of well bore fluids, successively inserting said units into said well bore, dropping said units freely at low falling velocity to produce a column of said liner units in nested relationship and curing said hardenable resin to form a continuous well liner structure wherein said thermo-setting resin comprises a resin portion and a curing agent, and wherein said resin portion is applied to one end of each of said well liner units and said curing agent is applied to the opposite end of each of said liner units.

References Cited by the Examiner UNITED STATES PATENTS 255,664 3/1882 Pettingill 166227 968,226 8/1910 Ziller 166-228 1,521,809 1/1925 Green 166227 2,167,191 7/1939 Vietti et al 166228 X 2,597,554 5/1952 West 16620 2,757,743 8/1956 Lillie et al. 166-227 2,823,753 2/1958 Henderson et al 16620 2,933,137 4/1960 DAndiffret et al. 166227 X 2,943,680 7/1960 Scott et al. 166-21 2,978,033 4/1961 Pitcher et al. 166228 CHARLES E. OCONNELL, Primary Examiner.

BENJAMIN BENDETT, Examiner.

R. W. COLLINS, T. A. ZALENSKI, Assistant Examiners. 

1. A WELL LINER CONSISTING AS THE COMPLETE STRUCTURE OF COMMINUTED SHELL CEMENTED WITH AN INSOLUBLE BINDING AGENT, SAID LINER BEING A SELF-SUPPORTING CYLINDER HAVING A BORE DISPOSED ALONG THE AXIS THEREOF AND CHARACTERIZED BY HAVING HIGHLY PERMEABLE EXTERIOR AND INTERIOR CYLINDRICAL WALLS OF THE CEMENTED COMMINUTED SHELL FREE FROM ANY CONFINING SUPPORTING METAL STRUCTURE AND OF SUFFICIENT STRENGTH IN THE COMMINUTED SHELL STRUCTURE PER SE TO WITHSTAND USE WITHIN A WELL BORE. 